Biomarkers are cellular, biochemical, or molecular alterations that can be easily and non-invasively measured in human tissues and are directly or indirectly in the pathway of disease. Air particulate pollution, also known as particulate matter (PM), induces lung and systemic inflammation and acute reductions in lung function and accelerated lung aging. The limited availability of biomarkers that reflect at-risk exposures and preclinical effects on lung function dramatically limits opportunities for effective targeted prevention. To address this gap, our long-term goal is to identify novel biomarkers that reflect environmental influences and predict the risk of impaired lung function. We will leverage experimental and clinical evidence on the roles of Extracellular Vesicles (EVs)-i.e., tiny membrane-bound vesicles actively released by human cells into the bloodstream- and of their bioactive cargo of microRNAs (miRNAs) as conveyors of inflammatory responses. Animal and human studies have shown that PM induces release of EVs into the bloodstream from the lung and other relevant tissues. In particular, PM causes release of EV-encapsulated miRNAs, which are key bioactive molecules that can control the expression of genes in recipient cells. Yet to date, no data are available on EV biomarkers as part of the mechanistic paths linking PM exposure to its adverse effects on lung function. In this proposal, we will leverage the resources of two well-phenotyped longitudinal cohorts, the Normative Aging Study (NAS, n=750) and the Cooperative Health Research in the Region Augsburg (KORA), our replication partner cohort (n=750 in the proposed replication set). In both NAS and KORA, we have access to repeated collections of blood samples, exposure data, and lung function measurements from serial visits over ~10 years of follow up. We hypothesize that the number, size, and miRNA cargo of blood EVs are modified in response to short- and/or long-term exposures to ambient PM (Aim 1); and that the EV number, size, and miRNA cargo are altered in individuals with lower lung function in blood samples concurrent to lung function testing (Aim 2.a) and/or in serial samples collected up to 10 years before the most recent lung function testing (Aim 2.b). We will establish and make publicly available a reference dataset on the tissue/cell type of origin of blood EVs and of their miRNAs; we will use this dataset to estimate the sources of EV-encapsulated miRNAs linking PM to impaired lung function (Exploratory Aim 3.a); we will use causal modeling to determine whether EV biomarkers affect blood messenger RNA expression, are linked to inflammation markers, and predict- through mediation or modification-PM effects on lung function (Exploratory Aim 3.b). Across aims, we will use detailed characterization of PM chemical components to capture their emission sources. Exposure assessment will also be informed by indoor measurements at 356 of the NAS participants' homes. EVs have increasingly recognized roles in health and disease. Therefore, our research may yield a model that could be eventually applied to additional respiratory risk factors and other age-related ailments.